Noncorrosive mineral oil



, recent years.

Patented Aug. 31, 1954 UNITED STATES PATENT OFFIC Jones, Irvington, N. Y., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application February 14, 1952, Serial No. 271,637

6 Claims. 1

This invention relates to mineral lubricating oils. Particularly the invention relates to mineral lubricating oils that are adapted for use in aircraft engines of the reciprocating type. More particularly the invention relates to highly refined aviation engine oils having a desirably low corrosivity to finely machined metal parts containing copper alloys, such as bronze valve guides, etc., which operate at high temperatures in modern reciprocating aircraft engines.

The development of special lubricants for specific lubricating requirements has been rapid in With the increase in performance of high speed machinery, there has been an increase in severity of requirements for special lubricants and. the lubrication art has kept pace with the demands placed upon it. Of particular note is the aviation industry where rapid. technical development of high speed engines has called for more highly specialized lubricants that must perform satisfactorily under a wide range of operation conditions. As a result aviation engine lubrication has become a highly specialized problem and a great deal of effort in the lubrication industry has been directed toward its solution.

A great deal of trouble has been experienced with aviation engine oils in regard to their tendency to corrode the bronze exhaust valve guides present in a number of the reciprocating engines used by the aircraft industry. This corrosivity results in undue wear of the valve guides with a corresponding shorter engine life, increase in number of non-operating hours in the life of the engine, etc. Since the temperature of the exhaust valves is in the neighborhood of from about 300 to 600 0., it is seen that this problem is a very serious ones and is one to which a great deal of attention is being given. It is toward this problem that the instant invention is directed.

The oils prepared for use in aviation engines are representative of the most highly refined oils available. Due to the extremely high requirements of these lubricants, the components of aviation engine oils are normally propane deasphalted, phenol extracted, dewaxed, acid treated, and clay contacted. By the ordinarily accepted tests these oils were shown to be substantially non-corrosive. However, it has been found that even these highly refined oils are corrosive to bronze at temperatures existent in aviation engine operation.

It has now been found and forms the object of this invention that the reduction of the bronze corrosivity of these highly refined engine oils may 2 be accomplished by a process which comprise treating the lubricating oil with an oxide of lead, at elevated temperatures in a manner suflicient to maintain intimate contact between the oxide and the oil. The treatment is carried'out for a period of time which varies with the particular lubricating oil used and the temperature employed. After treatment the oil is cooled and can be filtered with or without the use of filter aids such as Hy-fio to remove sediment, and additive materials, if desired, may be added. It is also contemplated to treat the oil with the lead oxide by various other methods known to the art. For instance, the oil may be percolated through a bed of the lead oxide, so long as sufficient contact is obtained. 7

The art of lubricating oil manufacture is familiar with advantages of treating mineral oils with oxides of the heavy metals. For instance, in United States Patent No. 1,581,369 it is taught that sulfur and sulfur-containing bodies may be removed from an oil stock containing them by treatment with a lead oxide, specifically PM). It is also taught in United States Patent 1,886,261 that oil or gasoline stocks may be treated with metallic oxides generally to sweeten, or to meet other specifications excepting gum residue requirements. The use of a filter bed containing lead oxide in conjunction with fullers earth and sodium hydroxide to remove residues after the well known doctor sweetening process is taught in United States Patent 1,903,094. A refinement in the method of removing sulfur and sulfur compounds from oil stocks by treating with metallic oxides is-taught in United States Patent 2,276,526. These disclosures, however, teach the removal of contaminants such as sulfur or sulfurcontaining compounds from oils that contain a relatively high percentage of these undesirable components, that is to say, a relatively unrefined oil. As will be further pointed out below, the treatment of the instant invention is performed on a highly refined stock and there is substantially no reduction in the low sulfur content remaining after the refining procedures to which the oil has previously been subjected.

In general, the aviation engine oils contemplated herein are those highly refined oils having a viscosity at 210 F. of from about 55 to 150 S. U. S. Experience has shown that outstanding aviation engine oils are advantageously prepared by blending various bright stocks with lighter oils, the blend combining desirable characteristics of both components. Blends having a viscosity of from to S. U. S. at 210 F. are especially adapted for use in the instant. invention. 1

The various lead oxides operable in the process of this invention include plumbous oxide (PbO) plumbous plumbite (PbzOs), plumbous plumbate (1 13304), or plumbous peroxide (PbOz) The amount of the lead oxide used in the treatment of this invention will depend upon the particular lubricant and its natural or original corrosivity. Generally speaking, from 0.10% to 2.0% by weight, based on the weight of the mineral oil, will be used, with from 0.50% to 1.5% being sufficient for most oils. The latter range is contemplated in the preferred embodiment.

The temperature of the treatment will ordinarily vary between about 250 to 750 F. with best results with most aviation engine oils being obtained by treating temperatures within the range of from 400 to 600 F. During the heating of the mixture of lead oxide and mineral oil intimate contact between the liquid and the oxide must occur. This contact may be accomplished by any of the various methods known to the art. The time of the treatment of this invention will vary again with the aviation engine oil being treated. For most oils treatment with from 0.10% to 2.0% of red lead oxide for from 0.25 to 6 hours at temperatures ranging from 250 to 750 F. will result in products of desirably low corrosivity. In most cases 1 to 2 hours of treating time will be sufiicient.

In order to more explicitly define the instant invention the following illustrative examples are given.

EXAMPLE I A high quality, highly refined mineral lubrieating oil blend having a viscosity at 210 F. of 102.4 S. U. S., hereinafter referred to as oil A, was prepared by admixing a deasphalted, dewaxed,

guide was carefully cleaned and its weight determined. The test specimen was then immersed in the sample of oil to be tested and the temperature raised to 650 F. and maintained at that temperature for 17 hours. After the test period the loss of weight of the test specimen was determined and reported as milligrams weight loss per gram of metal.

The results of these tests, reported in milligram loss in bearing weight per gram are set out in Table I below.

EXANLPLE II Example I was repeated using as the test oil a blend having a viscosity of 100 S. U. S. at 210 F. and a. viscosity index of 99. This blend was similar to oil A but was prepared from a highly refined West Texas Light bright stock combined with the same Mid-Continent distillate oil used in Example I. This blend, hereinafter referred to as oil B, contained only 0.19 weight percent sulfur and was non-corrosive to copper, giving a Cu strip rating of 2. It was divided into portions and submitted to the process of invention using various conditions and submitted to the same bronze corrosion test as described above. Test results are given in Table I below.

EXAMPLE III The oil used in this example, oil C, was a dewaxed, clay-treated, phenol-extracted Mid-Continent distillate having a viscosity at 210 F. of 59 S. U. S. It contained only .24 weight percent of sulfur and was non-corrosive having a copper strip corrosion test rating of 2. Bronze corrosion test data before and after treatment with the process of this invention are set out in Table I below.

Table I LEAD OXIDE TREATMENT OF MINERAL OILS Mineral Oil Percent Lead Oxid Bronze Corrosion est (wt. loss, mgmJgm.)

Treating Time, Hrs.

Treating Percent 2 Sulfur Ash,

Percent Percent Pb 99. 99999995 99999??? Hb- WNHUVONQBO Writ: O

cncn

acid-treated, clay-contacted, phenol-extracted Panhandle bright stock with a dewaxed, claytreated, phenol-extracted Mid-Continent distillate oil. This blend contained only 0.32 weight percent sulfur, little or none of which was cor rosive, as indicated by the fact that in the standard Cu strip corrosion test it had a rating of 2, which is barely distinguishable from an unused Cu strip. Nevertheless, it did give measurable corrosion to bronze. The blend was divided into portions and treated in accordance with the process of the invention described above.

As a measure of the corrosivity of the oil samples to bronze they were submitted to a test which is briefly described as follows:

A quarter section of a regulation bronze valve It will be noted from the data of Table I above that the corrosion loss is very markedly decreased by the process of invention. Oil A, having a corrosivity of 1.28 mg./gm. was reduced to 0.10 mg./gm. when 1% Pb304 was used and the temperature was maintained at 500 F. A temperatent of the finished product. In other words, no sulfur is removed or eliminated by the instant process, a solution to a new lubricating problem.

To summarize briefly, this invention relates to a process for the reduction of corrosivity of highly refined mineral lubricating oils useful in aircraft engines which comprises treating the oils with from 0.10% to lead oxide at a temperature of from 250 to 750 F. for from 0.25 to 6 hours without substantially decreasing the sulfur content of said oils.

What is claimed is:

1. A process for the reduction of bronze corrosivity of highly refined mineral oils containing substantially no corrosive sulfur which comprises treating said oils with from 0.1% to 2.0% by weight of Pb3O-4 at a temperature within a range of from 250 to 750 F. for a period of time of from 0.25 to 6 hours without removal of any substantial quantity of sulfur from said oil.

2. A process for the reduction of bronze corrosivity of highly refined mineral oils having viscosities at 210 F. ranging from 50 to 150 S. U. S. containing substantially no corrosive sulfur which comprises treating said oils with from 0.1% to 2.0% by weight of Pb304 at a temperature within a range of from 250 to 750 F. for a period of time of from 0.25 to 6 hours without removal of any substantial quantity of sulfur from said oil.

3. A process for the reduction of bronze corrosivity of highly refined mineral oils having viscosities at 210 F. ranging from 50 to 150 S. U. S. containing substantially no corrosive sulfur which comprises treating said oils with from 0.5% to 1.5% by weight of Pb3O4. at a temperature within a range of from 250 to 750 F. for a period of time of from 0.25 to 6 hours without removal of any substantial quantity of sulfur from said oil.

4. A process for the reduction of bronze corrosivity of highly refined mineral oils having viscosities at 210 F. ranging from to 150 S. U. S. containing substantially no corrosive sulfur which comprises treating said oils with from 0.5% to 1.5% by Weight of PbsO4 at a temperature within a range of from 400 to 600 F. for a period of time of from 0.25 to 6 hours without removal of any substantial quantity of sulfur from said oil.

5. A process for the reduction of bronze corrosivity of highly refined mineral oils having viscosities at 210 F. ranging from 50 to 150 S. U. .8. containing substantially no corrosive sulfur which comprises treating said oils with from 0.5% to 1.5% by weight of Pb304 at a temperature within a range of from 400 to 600 F. for a period of time of from 1 to 2 hours without removal of any substantial quantity of sulfur from said oil.

6. A process for the reduction of bronze corrosivity of a propane deasphalted, phenol extracted, acid treated, clay-contacted mineral oil blend having a viscosity at 210 F. within a range of from to S. U. S. and containing substantially no corrosive sulfur, which comprises treating said blend with from 0.5% to 1.5% by weight of Pb304 at a temperature within a range of from 400 to 600 F. for from 1 to 2 hours without removal of substantial quantities of sulfur from said oil blend and without the addition of any substantial quantity of lead thereto.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 534,295 Suckert Feb. 19, 1895 2,392,853 Kinsel Jan. 15, 1946 

1. A PROCESS FOR THE REDUCTION OF BRONZE CORROSIVITY OF HIGHLY DEFINED MINERAL OILS CONTAINING SUBSTANTIALLY NO CORROSIVE SULFUR WHICH COMPRISES TREATING SAID OILS WITH FROM 0.1% TO 2.0% BY WEIGHT OF PB3O4 AT A TEMPERATURE WITHIN A RANGE OF FROM 250* TO 750* F. FOR A PERIOD OF TIME OF FROM 0.25 TO 6 HOURS WITHOUT REMOVAL OF ANY SUBSTANTIAL QUANTITY OF SULFUR FROM SAID OIL. 